Compositions which can be used to impart electroconductive properties to thin films, such as, polymer films, magnetic recording tapes, paints, among others, are not always economically attractive or reliable. For example, electroconductive compositions, e.g., powders known as ECPs, which are currently available for use as conductive pigments in paint are not completely effective. Carbon black can be used to impart electroconductivity, but this can limit the color of a paint to black, dark gray and closely related shades. Conventional antimony-doped tin oxide powders may be used as an ECP, but the quantities required may result in unfavorable cost and color limitations.
An electroconductive composition which comprises antimony-containing tin oxide wherein the tin oxide is predominantly crystalline, and the composition is associated with silica or a silica-containing material, e.g., a silicate, is described in European Patent Application Publication No. 0359569, which published on Mar. 21, 1990, and is entitled "IMPROVED ELECTROCONDUCTIVE COMPOSITION AND PROCESS OF PREPARATION" (hereinafter referred to as "EPO '569"). The entire content of EPO '569 is hereby incorporated by reference. The antimony-containing tin oxide forms a two-dimensional network of densely packed crystallites upon the surface of the silica or a silica-containing material. The silica or silica containing material is a powder comprising shaped particles of amorphous silica, inert core particles coated with amorphous silica or hollow shells composed of amorphous silica. In the process used to prepare this electroconductive composition, the silica is first deposited as a coating upon core particles, which are in an aqueous suspension; optionally the core particles may then be dissolved, and the antimony-containing tin oxide layer is deposited on the silica surface as an additional step in the process.